Stable lubricating composition



Patented Nov. 21, 1944 OFFICE STABLE LUBRICATIN G COMPOSITION Arnold J.Mot-way,

Clark Township,

Union County, and John C. Zimmer, Union, N. 3., assignor to Standard OilDevelopment Company, a corporation of Delaware No Drawing. ApplicationDecember 30, 1941, Serial No. 424,926

.- 13 Claims.

The present invention relates to improved stable lubricatingcompositions, particularly lubricating greases stable against oxidation.More particularly, the invention relates to grease compositions suitablefor the lubrication of anti-friction bearings, such as ball bearings androller bearings.

Grease manufacturers as well as the manufacturers of machine partsrealize that greases which are easily oxidized soon lose theirlubricating value due to hardening, and the products of oxidation arecorrosive to the machine parts. Greases should be stable over a longperiod of time so that in storage they will not oxidize and break downto liberate corrosive products. It is the practice of anti-frictionbearing manufacturers to store their product packed with lubricant. Ifduring storage this lubricant breaks down due to oxidation, corrosiveacids are liberated which cause corrosion of the bearing with resultantsticking or locking of the hearing by corrosion products. In operation,the bearing, although of the anti-friction type, does have somefriction, and operating at high speeds generates heat which raises thetemperature of the hearing appreciably above the temperature of thesurrounding atmosphere. Unless precaution is taken, this highertemperature will cause a lubricant to oxidize, depositing a coating ofso-called varnish over the surface of the bearing. This varnish is gummyand sticky and gradually hardening and reduces the efficiency of thebearing, or even causes it to lock or freeze, thus rendering it useless.It is customary to put antifriction bearings in operation in a. widevariety of places where a likewise wide variety of temperatureconditions prevail. Lubricated-forslife bearings are now being used in anumber of inaccessible places, and it is obvious that the life of thebearing and the machine will depend on the life of the lubricant.The'lubricant must therefore be capable of withstanding a wide variationin temperature without oxidation, gum formation, or the loss oflubricating value. Freedom from oxidation is a desirable characteristicnot only in greases for life-time bearings, but for greases in generalas well. Besides being chemically stable, greases should not separatephysically. This phenomenon of physicalseparation is known as bleeding.

Recognizing the desirability of preventing in so far as possible theoxidation of greases and the ensuing detrimental results, it has becomethe practice to add an oxidation inhibitor to greases. In the usual typeof grease prepared from calcium and/or sodium soaps, particularly whensuch greases have an alkaline reaction, most of these inhibitors arefairly effective and prevent oxidation to a considerable degree.However, greases prepared on the acid side, i. e., having an acidreaction, are not appreciably stabilized against oxidation by theoxidation inhibitors found to be most effective in an alkaline grease.

The most effective and generally accepted test for oxidation is theNorma-Hofimann bomb test described in the paper An Accelerated OxidationTest for Chemical Stability of Lubricating Greases" by F. L. Wrightpresented before the 4th Annual Convention of the National Associationof Lubricating Grease Manufacturers Inc,

, October 12-13, 1936. By this test, using a glass catalyst, a grease tobe considered stable against oxidation should withstand 100 hours at 210F.

'with no more than a 5 lb. drop in oxygen pressure.

stabilize acid reacting greases against oxidation This and other objectsof the invention will be apparent from the following description.

It has now been discovered that the addition of both phenylalpha-naphthylamine and a zinc soap to an acid reacting greaseeffectively stabilizes the grease against oxidation. Phenyl'alpha-naphthylamine has been used effectively in basic greases as ananti-oxidant but has been found to be relatively ineffective in an acidgrease. The zinc soaps have not heretofore been looked upon as havingany anti-oxidant properties rather as oxidation accelerators incatalysts.

Although a wide range of lubricating oils may be employed, in general,the base oil comprises an oil having a viscosity in a range of fromabout 35 to 1100 seconds at 210 F., a viscosity index of above 20 Deaneand Davis, and a good resistance to oxidation. However, in preparing thecompositions of this invention, it is preferred to use a base oil havinga viscosity of from 40 to 55 seconds S. U. V. at 210 F.

The acids utilized for the production of the metal soaps used in themaking of the grease may be either hydrogenated fish oil acids,palmitic, stearic, oleic, naphthenlc acids, or oxidized wax acids, orany other fatty acid or fat commonly used as a soap stock. The metal ionof such as lithium. It is preferred, however, to use a mixture oflithium and aluminum soaps consisting of a'major proportion of lithiumsoap and a minor proportion of aluminum soap.

Any of the methods generally used in the production or acid greasescontaining fromv 10 to 35% soap are suitable here. The acid soaps may bemade separately and then incorporated in the oil. However, customarilythe soap stock .is dissolved in a portion of the lubricating oil bymeans of gentle heating and stirring. Sumcient metal hydroxide or otherwater-soluble salt of the metal to neutralize the soap stock is thenadded and the mixture stirred until the reaction is complete,

after which suiilcient fatty acid is added to give an acid reaction oran amount of metal hydroxide may beuse'd for the neutralization of thesoap stock which will incompletely neutralize the soap stock leaving themixture with a slight acid reacv tions may be secured by varying thesoap content of the grease in a particular oil within the limitsspecified, or by manipulating both the soap content and the viscosity ofthe lubricating base oil.

The anti-oxidantsused in accordance with this invention consist of amixture of phenyl a-naphthylamine, phenyl beta naphthylamine or.diphenylamine and a zinc soap such as zinc phenyl stearate. Theproportion of combined anti-oxi-' dants ranges from about 0.5% to 2% byweight of the grease. The amount of phenyl a-naphthylamine used willrange between 0.1 and 1% and the amount of zinc soap between 0.4 and1.5%. In the formation of the zinc soaps, any of the acids previouslyenumerated may be used although it is preferred to use naphthenicacid.Among the many zinc soaps found to be useful for the purposes of thisinvention, zinc stearateseems'to occupy a unique position in that whileit is equally eflicaceous in enhancing the inhibiting power of phenyla-naphthylamine in acid greases, it is not recommended for general usefor the reason that it has a somewhat adverse effect on the greasestructure causing the grease to be soft and separate some oil.

The following examples will serve to illustrate specific embodiments ofthe invention:

Exmrm 1 55 point oil) Hyd fed fish n ms Percent V Phenyl a-naphthylamine0.2 ro'gena ac 13.00 LiOH (54% lithium hydroxide) 2.05 Mb we Aluminumstearate 0.50 Hours Zinc naphthenate 0.50 '5# drop 18 Lulgricating oil(low. pour Coastal oil) 41.875 15# drop 62' Lu ricating oil (lowviscosity, low pour point oil) 41.875 P t Phe la-na hth lamine .2 cm W py o a Hydrogenated fish oil acids 13.00 65 LloH I 2.05 Aluminum stearate05' In compounding the above formulafthe acid and approximatelyone-quarter of the oil are charged into a fire-heated kettle equippedwith agitators. The mixture is then heated and stirred to a temperatureof about 150 F. 'or until all the acid is melted and dissolved in theoil, and then the lithium hydroxide, dissolved in boiling water, isadded to the acid-oil solution. Heating and agitation is continued andthe temperature permitted to slowly rise until it reaches about 200 1''.The aluminum stearate is then added and the heating and stirringcontinued along with intermittent additions of lubricating oil until allbut a small portion or the oil has been included. Heating and stirringis'continued until the grease becomes fluid, about 370 F. The phenyla-naphthylamine and zinc naphthenate dissolved inthe remainder of theoil are then added, heating is then discontinued and the grease stirreduntil the temperature has dropped to below 100 F. The grease is thendrawn. This grease, when tested in the Norma Hofimann oxidation bomb,showed a 5 lb. drop in pressure after 132 hours.

EXAMPLE 2 Per cent Hydrogenated fish oil acids 13.00 L1OH,(54=% lithiumhydroxide) 2.05 Aluminum stearate 0.5

Zinc steara 0.5 Phenyl a-naphthylamine 0.5 Lubricating oil (low pourCoastal oil) 41.725 Lubricating oil (low viscosity, low pour point oil)41.725

' This composition wascompounded as outlined in Example 1.

Norma Hofimann bomb oxidation life Hours 5# drop 300 13#'drop 500 Forthe purpose oi! ready comparison, the following formulae were compoundedaccording to the method outlined in Example 1 and tested in the NormaHofimann bomb, giving the following 3 results: I

- Per cent Hydrogenated fish oil acids 13.00 LioH 2.05 40 Aluminum,stearate 0.5

Lubricating oil (low pour Coastal oil) 42.225 Lubricating oil (lowviscosity, low pour Lubricating oil (low pour Coastal oil) 42.125

Lubricating oil (low viscosity, low pour Phenyl a-naphthylamineLubricating oil (low pour Coastal oil) 41.97 Lubricating oil (lowviscosity, low pour point oil 41.975

Norma Hofimann bomb oxidation life H 5# drop 75 .l0# drop EXAMPLE 6 Percent Hydrogenated fish oil acids 13.00 LioH 2.05 Aluminum stearate 0.5Zinc naphthenate 0.5 Lubricatingoil (low pour Coastal oil) H.975Lubricating all (low viscosity, low pour point oil 41.975

Norma Hofimann bomb oxidation life Hours l4# drop What is claimed is:

1. An improved stable grease composition comprising a minerallubricating oil, iii-35% of metal soap, a slight excess of higheriattyacid."

and .5-2% oi an oxidation inhibitor consisting of a mixture oi from.l-l% of an oil-soluble organic amine selected from the group consistingof phenyl alphamaphthylamine, phenyl betanaphthylamine di phenylamineand from .d-l.5% of a zinc soap.

2. An improved stable greasecomposition comprising a mineral lubricatingoil, ill-35% of metal scan, a slight excess oi free higher fatty acid,and .5-2% of an oxidation inhibitor consistin of a mixture of from .l-l%or an oil-soluble aromatic amine selected from the group consisting ofphenyl alpha-naphthylamine, phenyl betanaphthylamine and di-phenylamineand from .4=l.5% of zinc naphthenate.

3. An improved stable grease composition comprising a minerallubricating oil, 10-35%'of a mixture of lithium and aluminum soaps, aslight excess of free higher fatty acid, and .5-2% of an oxidationinhibitor consisting of a mixture of .1l% of phenyl a-naphthylamine and.*1.5% or a zinc soap.

4:. An improved stable grease composition comprising a minerallubricating oil, 10-35% of a mixture of lithium and aluminum soaps, aslight excess of free higher fatty acid, and .5-2% of an oxidationinhibitor consisting of a mixture of .l-1% of phenyl beta naphthylamineand .4-1.5% of a zinc soap.

5. An improved stable grease composition comprising a minerallubricating 011, 10-35% of a lithium soap, a slight excess of freehigher fatty acid, and .5-2% of an oxidation inhibitor consistlng of a.mixture of .1-1% of phenyl a-naphthylamlne and .51.5% of a zinc soap.

7. An improved stable grease composition comprising a minerallubricating oil, 10-35% of lithium soaps of the hydrogenated fish oilacids, a slight excess of freehigher fatty acid, and .5-2% of anoxidation inhibitor consisting of a mixture of .1-1% of phenyla-naphthylamine and .4-1.5% of a Zinc soap.

8. An improved stable grease composition comprising a minerallubricating oil, 10-35% of a metal soap, a. slight excess ofhydrogenated fish oil acids, and .5-2% of an oxidation inhibitorconsisting of a. mixture of .1-1% of phenyl anaphthylamine and .41.5% ofa zinc soap of phenyl stearic acid.

9. An improved'stablegrease-composition eonsisting of a low viscosity,low pour mineral lubrislstlng of a. mixture of .1-1% of phenyl a-naph--thylamine and .41.5% of a zinc soap.

6. An improved stable grease composition comprising a minerallubricating oil, 10-35% of lithium soaps of the hydrogenated fish oilacids and aluminum stearate, a slight excess of free acid, and .5-2% ofan oxidation inhibitor concating oil, 15.5% of a mixture of lithium andaluminum soaps, a slight excess of free higher fatty acid, and 1% of anoxidation inhibitor consisting of .5% phenyLa-naphthylamine and .5% of azinc soon;

10. An improved stable grease composition consisting of a low viscosity,low pour mineral lubricating oil, 15% lithium soaps of hydrogenated fishoil acids, 0.5% of aluminum stearate, a slight excess of hydrogenatedfish oil acids, and 1% of an oxidation inhibitor consisting of .5%phenyl a-naphthylamine and .5% of a zinc scan.

11. An improved stable grease composition consisting of a low viscosity,low pour mineral lubrieating oil, 15% lithium soaps of hydrogenated fishoil acids, a slight excess of hydrogenated fish oil acids, and 1% of anoxidation inhibitor consisting of .5% phenyl a-naphthylamine and .5% ofa zinc oleate.

12. An improved stable grease composition con slsting of a lowviscosity, low pour mineral lubricating oil, 15.5% of a mixture oflithium and aluminum soaps, a slight excess of free higher fatty acid,and as an oxidation inhibitor, 0.5% phenyl a-naphthylamine and 0.5% ofzinc naphthenate.

13. In a grease composition comprising a mineral lubricating oil, greaseproducing amounts of metal soap and a slight excess of free highermolecular weight fatty acid, the improvement which consists inincorporating in the grease a small amount, sufficient to inhibitdeterioration of the grease, of an oxidation inhibitor consisting of amixture of from .1-1% of an oilsoluble organic amine selected from thegroup consisting of phenyl a-naphthylamine, phenyl bnaphthylamine anddi-phenylamine, and .4-1.5%

of a. zinc soap.

ARNOLD J. MORWAY. JOHN C. ZIMMER.

